The present invention relates generally to electronic energy meters, and more particularly to highly functional programmable electronic energy meters with systems for service identification and power quality analysis.
Programmable electronic energy meters are rapidly replacing electromechanical meters due to the enhanced functionality achieved using programmable logic integrated into solid-state electronic meters. Some of these meters can be used to meter various different electrical services without hardware modification. For example, meters having a voltage operating range between 98 Vrms to 526 Vrms are capable of operation with either 120 V or 480 V services. U.S. Pat. No. 5,457,621, dated Oct. 10, 1995, entitled SWITCHING POWER SUPPLY HAVING VOLTAGE BLOCKING CLAMP, assigned to ABB Power T and D Company discloses examples of such meters. In addition, some meters are constructed for use with any 3-wire or any 4-wire service, also disclosed in U.S. Pat. No. 5,457,621. Unless meters having this versatility are used, utilities must be careful to install the correct meter in relation to both configuration and electrical service supplied at the installation site. Unfortunately, meter installers are not always trained to detect or note service particularities which might indicate that the meter to be installed is not configured properly for a particular installation.
For this reason, some utilities configure the meters themselves to ensure better control over which meters are installed at which installation sites. However, such configuration activity adds to the installation cost and does not always reduce the risk that a meter configured for one service might inadvertently be installed at a site supplied by a different service. Therefore, there remains a need for an electronic meter which automatically detects the service type and voltage to which the meter is installed and which either automatically configures its own programming to the detected service or provides a simple means for manual configuration at the installation site.
Further, the performance of power quality tests requires that the type of service and service voltage be known prior to installation so that the meter""s programming can be locked to the appropriate service-dependent thresholds utilized in connection with particularized power quality tests. Therefore, for this additional reason, there remains a need for an electronic meter to automatically detect the service type and voltage to which the meter is installed and which automatically configures its programming to the detected service.
In addition, many new electronic energy meters have begun to take advantage of their programming capabilities by providing limited diagnostic and/or power quality testing. These capabilities are provided by programming stored in read only memory (ROM). Thus, these meters are currently limited in operation to predefined programming, such as predefined sets of tests. Significantly, such meters are also limited to the measurement of only a predetermined set of parameters that have been programmed into such meters, i.e., stored in ROM, during manufacture. Consequently, any change to the measurements or tests supported by the meter must be carried out by replacing the meter""s ROM, i.e., by factory modification. Therefore, there also exists a need for a more flexible electronic energy meter that permits the addition of new measurements or testing capabilities without requiring factory modifications to effect such functionality changes.
The meter includes firmware which measures the characteristics of electrical energy supplied to the meter and which generates characteristic signals reflective of the measured characteristics of the electrical energy. A processor is connected to receive and process the characteristic signals. The processing of the characteristic signals includes selecting and manipulating certain of the characteristic signals and generating characteristic information in response to the selection and generating additional characteristic information in response to the manipulation. It is preferred for the meter to include a memory having reference information stored therein. In such an embodiment, the manipulation of characteristic signals includes retrieving certain of the reference information and generating the characteristic information in response to the selected signals and the reference information.
The present invention is directed to a system for monitoring near-instantaneous system parameters of electrical energy having at least one phase provided to an energy meter via a service type, comprising: storage means for storing reference information reflective of different service types; means for measuring characteristics of the electrical energy; and means for retrieving the reference information from the storage means and determining the near-instantaneous system parameters responsive to the reference information for the service type and the measured characteristics.
According to aspects of the present invention, the characteristics are derived from phase voltage and phase current, and the characteristics are measured for a predetermined amount of time. The predetermined amount of time is programmable, and preferably comprises a predetermined number of line cycles.
In accordance with further aspects of the present invention, memory means are provided for recording the near-instantaneous system parameters. Preferably, the storage means comprises an EEPROM and the memory means comprises a RAM. The EEPROM stores at least one threshold that is preferably programmable. The threshold comprises at least one of time, voltage, current, and power factor, and can be responsive to the service type which provides electrical energy to the energy meter. Alternatively, the threshold can be independent of the service type which provides electrical energy to the energy meter.
In accordance with a further aspect of the present invention, an indicator and means for activating the indicator responsive to the threshold being surpassed by at least one of the near-instantaneous system parameters stored in the memory is provided.
In accordance with a further aspect of the present invention, display means are provided for displaying the near-instantaneous system parameters.
According to further aspects of the invention, the means for measuring comprises a digital signal processor (DSP), and the means for retrieving and determining comprises a microcontroller.
According to one aspect of the present invention, the near-instantaneous system parameters comprise at least one of frequency, power, arithmetic kVAR, vectorial kVAR, arithmetic kVA, vectorial kVA, phase angle, current to voltage angle, arithmetic system power factor, vectorial system power factor, phase voltage, phase current, phase power factor, phase current to phase voltage angle, phase kW, phase kVA, phase kVAR, total harmonic distortion, second harmonic current distortion, general Nth voltage harmonic magnitude, and general Nth current harmonic magnitude.
In accordance with further aspects of the present invention, the near-instantaneous system parameters are selectable via one of optical communications and electronically from an external source, and the means for determining the near-instantaneous system parameters comprises programmable conversion routines. The service type is single phase or multiphase, and the near-instantaneous system parameters are determined for each phase when the service is multiphase.
In accordance with further aspects of the present invention, means are provided for activating the means for measuring characteristics of the electrical energy. The means for activating are user-activated. The means for activating activates the means for measuring responsive to a priority scheme.
In accordance with a further aspect of the present invention, means are provided for linking at least two of the measured characteristics. The near-instantaneous system parameters are determined responsive to the linked measured characteristics.
Another embodiment within the scope of this invention includes an electronic processor-implemented process for monitoring near-instantaneous system parameters of electrical energy provided to an energy meter via a service type, comprising the steps of: storing reference information in a memory reflective of different service types; measuring characteristics of the electrical energy provided to the energy meter; and retrieving the reference information from the memory and determining the near-instantaneous system parameters responsive to the reference information for the service type and the measured characteristics.
According to another aspect of the present invention, the process further comprises the step of recording the near-instantaneous system parameters in a second memory. The process further comprises the step of activating an indicator responsive to the threshold being surpassed.
According to another aspect of the present invention, the process further comprises the step of displaying the near-instantaneous system parameters.
According to another aspect of the present invention, the process further comprises the step of selecting the near-instantaneous system parameters via one of optical communications and electronically from an external source.
According to another aspect of the present invention, the step of determining the near-instantaneous system parameters comprises converting the reference information and the measured characteristics using programmable conversion routines.
According to another aspect of the present invention, the process further comprises the step of linking at least two of the measured characteristics, the near-instantaneous system parameters being determined responsive to the linked measured characteristics.